The present invention relates to agricultural crop harvesting machines, such as round or rectangular balers, loader wagons, combine or forage harvesters, having a pick-up mechanism for lifting crop material such as hay, straw or silage grass from a field and delivering it to a crop collecting and/or processing apparatus. More particularly the invention pertains to a movable retainer screen or windguard which is mounted above the guide surface of the pick-up mechanism for keeping the crop in contact with a feeder means and providing an even flow to the collecting or processing apparatus, while preventing the crop material from being blown off the pick-up.
Conventionally, retainer screens or windguards comprise a bar extending across the pick-up mechanism with a plurality of tines attached thereto along the length of the bar, the tines extending rearwardly over the pick-up mechanism. Usually the windguard has no fixed position to the pick-up, but it can be moved upwardly by the material which has been picked up from a windrow and is being conveyed over the pick-up. Such movable windguard is disclosed by U. S. Pat. No. 4,411,127, in which the windguard automatically adjusts its position to the amount of the picked up material to prevent plugging of the pick-up when a larger windrow is encountered. On the other hand, when a small windrow is harvested, the windguard will lower and still ensure an adequate engagement of the crop by the pick-up tines and provide protection from the effects of the wind. Such movable windguard may be forced downwardly by gravity as described in U. S. Pat. No. 4,411,127 or by a spring.
It has been experienced that a movable windguard not always succeeds in smoothing out the crop flow and in providing an even flow to the mouth of the harvesting machine. When irregular patches of crop material are picked up, the windguard is thrown upwardly and looses contact with the surface of the crop layer. This hampers the regular flow of the crop material and exposes it to the action of the wind. Moreover, the top portion of the flow is not properly engaged by the pick-up tines. In some cases the tines may be thrown up that vigorously that they contact a part of the harvesting machine which is mounted above the pickup, thereby inducing structural damage to this part and/or the windguard tines.